Hi there,
Just in case you didn't know about them, I thought I'd do a post on the IMIV ipod interface. They are a company from Canada that do Ipod interfaces for older model Volvo's if you'd prefer to keep the stock radio.
I have a V70 T5 2000 with a HU 603 and mine works great. I just ordered the new iphone compatible cable from them and it's brilliant.
They are a really good company, they deliver really quickly and they have awesome customer service. Their link is below.
http://www.imiv.ca/cms/
Cheers...
